1. Field of the Invention
The present invention relates to a computer program product, system, and method for populating a secondary cache with unmodified tracks in a primary cache when redirecting host access from a primary server to a secondary server.
2. Description of the Related Art
In a storage environment, primary and secondary storage servers may maintain mirror copy relationships, where a primary volume in a mirror copy relationship comprises the storage or volumes from which data is physically copied to a secondary volume. Failover programs, such as International Business Machine Corporation's (“IBM”) HyperSwap® which is a function in the z/OS® operating system, provides continuous availability for disk failures by maintaining the mirror copy relationships to provide synchronous copies of all primary disk volumes on one or more primary storage systems to one or more target (or secondary) storage systems. (HyperSwap is a registered trademark of IBM in countries throughout the world). When a disk failure is detected, code in the operating system identifies HyperSwap managed volumes and instead of failing the I/O request, HyperSwap switches (or swaps) information in internal control blocks so that the I/O request is driven against the secondary volume of the mirror copy relationship. Since the secondary volume is an identical copy of the primary volume prior to the failure, the I/O request will succeed with no impact to the program issuing the I/O request, which could be an application program or part of the operating system. This therefore masks the disk failure from the program and avoids an application and/or system outage. (IBM, HyperSwap, and z/OS are registered trademarks of IBM in many countries).
There is a need in the art for improved techniques for redirecting host access from a primary server to a secondary server.